Kisspeptin-10 facilitates a plasma membrane-driven calcium oscillator in gonadotropin-releasing hormone-1 neurons.
Kisspeptins, the natural ligands of the G-protein-coupled receptor (GPR)-54, are the most potent stimulators of GnRH-1 secretion and as such are critical to reproductive function. However, the mechanism by which kisspeptins enhance calcium-regulated neuropeptide secretion is not clear. In the present study, we used GnRH-1 neurons maintained in mice nasal explants to examine the expression and signaling of GPR54. Under basal conditions, GnRH-1 cells exhibited spontaneous baseline oscillations in intracellular calcium concentration ([Ca(2+)](i)), which were critically dependent on the operation of voltage-gated, tetrodotoxin (TTX)-sensitive sodium channels and were not coupled to calcium release from intracellular pools. Activation of native GPR54 by kisspeptin-10 initiated [Ca(2+)](i) oscillations in quiescent GnRH-1 cells, increased the frequency of calcium spiking in oscillating cells that led to summation of individual spikes into plateau-bursting type of calcium signals in a subset of active cells. These changes predominantly reflected the stimulatory effect of GPR54 activation on the plasma membrane oscillator activity via coupling of this receptor to phospholipase C signaling pathways. Both components of this pathway, inositol 1,3,4-trisphosphate and protein kinase C, contributed to the receptor-mediated modulation of baseline [Ca(2+)](i) oscillations. TTX and 2-aminoethyl diphenylborinate together abolished agonist-induced elevation in [Ca(2+)](i) in almost all cells, whereas flufenamic acid was less effective. Together these results indicate that a plasma membrane calcium oscillator is spontaneously operative in the majority of prenatal GnRH-1 neurons and is facilitated by kisspeptin-10 through phosphatidyl inositol diphosphate hydrolysis and depolarization of neurons by activating TTX-sensitive sodium channels and nonselective cationic channels.
Constantin
Stephanie
S
Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorder and Stroke/National Institutes of Health, Bethesda, Maryland 20892, USA.
Caligioni
Claudia Simone
CS
Stojilkovic
Stanko
S
Wray
Susan
S
D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D059648:Kisspeptins; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D011247:Pregnancy; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000074502:Receptors, Kisspeptin-1; D015398:Signal Transduction / Q000235:genetics; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
C106628:KISS1 protein, human; C492248:Kiss1r protein, mouse; D059648:Kisspeptins; D009842:Oligopeptides; D018129:Phosphatidylinositol Phosphates; D043562:Receptors, G-Protein-Coupled; D000074502:Receptors, Kisspeptin-1; D026941:Sodium Channel Blockers; D007987:Gonadotropin-Releasing Hormone; D013779:Tetrodotoxin